Description

This simulation illustrates how Kepler's species motrix idea combined with his concept of inertia to dictate the speed of planetary motions. The simulation shows the rotating Sun with spinning lines of force (or species) that push the planets along their orbits. The earth and another planet are shown in orbit around the Sun. The speed of a planet's motion is determined by the strength of the species (which decreases with distance from the Sun) as well as the planet's moles. Kepler's moles concept was something like our modern concept of inertial mass, but Kepler believed that inertia was resistance to motion (whereas our modern concept is that inertia is resistance to CHANGES in motion). Kepler was also working with an Aristotelian notion of force such that the speed (rather than acceleration, as in Newtonian physics) of an object is proportional to the force applied. Thus, the speed of a planet would be inversely proportional to the planet's moles

Controls allow the user to speed up the simulation, change the radius of the planet's orbit, or change the planet's moles.